This project is concentrating on the characterization of unbroken chromosomal DNA from bacteria and higher organisms. After lysis of the cells and disruption of the nuclear structure, the DNA is characterized by physico-chemical methods which recent developments have made available for work on the giant molecules obtained. The principal one of these methods is the use of a viscoelastometer, an instrument developed to measure both the viscosity and the viscoelastic recoil of dilute DNA solutions. These measurements can be carried out on impure lysis mixtures. It is also possible to use a viscoelastic radial migration effect to separate large from small DNA molecules in such mixtures. Studies on the techniques and the theory of the methods themselves are also being undertaken. Bibliographic references: Simplified Solution of the Kirkwood-Riseman Equations for the Intrinsic Viscosity of a Chain Macromolecule. B.H. Zimm, Die Makromolekulare Chemie, Suppl. 1, 441-444 (1975); Viscoelastic Characterization of Single-Stranded DNA from Escherichia Coli. E. L. Uhlenhopp and B. H. Zimm, Biophys. J. 15. 223-232 (1975).